The present invention pertains to an apparatus for threading metal into a heating device and for removing scales that form and flake from the metal during heating. More particularly, the present invention relates to an induction heater having a continuous belt that threads metal strip into the induction heater and removes metal scales that form and flake from the metal during heating.
Induction heating is used to heat metal pieces such as, strip, bars, slugs, billets, tubes, slabs, plate and the like, by passing the metal pieces through a pathway wherein the metal is heated by an induction coil. The purpose of the induction heating may be to permit hot rolling, annealing, hardening, brazing or soldering two parts together, or treating metal in some other manner.
One particular application of induction heaters involves their use in conjunction with the continuous casting of metal strip. Because metal strip is thin and wide having a large surface area, it cools quickly upon exiting a continuous caster. Therefore, an induction heater, such as a transverse flux coil, may be utilized to reheat the strip metal so that it can be properly rolled. A transverse flux coil is desirable because of its ability to operate in a relatively small space, and heat thin metal strip in the above Curie temperature range.
When induction heaters are utilized in conjunction with continuous casters, at least one problem arises. After the metal strip exits a continuous caster, it is soft and limp because it is hot. As a result, it is difficult to thread the metal strip horizontally through an induction heater such as a transverse flux coil. To date, there is no device that the applicant is aware of that effectively threads limp or soft metal through an induction heater. Thus, a need exists to provide such an apparatus.
An additional problem associated with induction heaters when used in any application involves the formation of metal scales during heating. All heating of metals causes at least some scale to form on the surfaces of the part undergoing treatment when the heating processes are carried out in an oxygen-containing environment such as air. Ambient air, containing oxygen reacts with the metal at elevated temperatures causing scales to form on the surface of the work-piece. As the induction heater continues to increase the temperature of the metal, the scales flake off or fall from the work-piece. The flaking off of scales into the induction heating device is an undesirable result since it often causes failure of the induction coils.
One of the most prevalent causes of failure resulting from flaking of metal scales involves short circuiting. The metal scales drop from the work-piece and accumulate between the work-piece and the inductor. As the scale builds up within the housing of the induction heater, they begin to span the space between the work-piece and the inductor. Thus, a complete circuit is formed therebetween. Since the work-piece is generally supported by metal support components of the induction heating apparatus which are grounded, a short circuit is completed to ground through the inductor and work-piece.
In an effort to alleviate some of the adverse effects accompanying a short circuit of the foregoing character, prior designs have provided a sensor for detecting a short circuit before significant damage is done. For example, in response to detection of a short circuit, a control circuit may be actuated to disconnect the inductor from its power supply. This causes the inductor to de-energize so that the necessary steps can be taken to remedy the short circuit condition. In addition, a control circuit may be rendered operable to preclude the work-piece from entering the induction heater.
While short circuit detection devices of the foregoing character advantageously serve to protect the inductor and/or work-piece from significant damage, a considerable amount of production time is lost in shutting down the apparatus and performing the necessary maintenance operations to clear the inductor area of the metal scales causing the short. Furthermore, once the inductor area is cleaned, it is only a matter of time before scale accumulation will again cause a short to ground requiring shut-down and additional maintenance.
Another attempt to solve the problems associated with the formation of scales during induction heating is disclosed in U.S. Pat. No. 3,745,293 (Seyfried). Seyfried teaches an induction heating apparatus having an auxiliary circuit operable to cause burning of metal scales disposed between the inductor and work-piece. Such burning is achieved by establishing a low voltage circuit through the inductor and work-piece and the metal scales therebetween. By maintaining the burn-out circuit at low voltage, the metal chips are burned away and the inductor is not energized in such a manner that the work-piece is heated prematurely.
Although Seyfried was an advance in the art, the device has several shortcomings. First, the device suffers from a significant decrease in production time. In operation, Seyfried allows the scales to accumulate until a shorting would occur. Then, it shuts off the primary circuit and activates the secondary circuit. The secondary circuit or auxiliary circuit burns and eliminates the metal scales. By shutting down the primary circuit and waiting for the secondary circuit to burn off the metal scales, significant production time is lost. An additional drawback of Seyfried is the complexity and therefore increased cost of the device. It requires an additional complicated circuit. If a problem arises with the auxiliary circuit, it will likely be a difficult problem to fix.
Accordingly, there is a need in the industry to provide for an improved apparatus capable of effectively threading soft or limp metal through an induction heater that is also capable of removing scales produced during heating. The present invention contemplates a new and improved apparatus having such advantages.
In accordance with the present invention there is provided a threading and metal scale removing device comprising a heating apparatus for heating a work-piece. The heating apparatus has an inlet through which the work-piece is threaded and an outlet through which the work-piece exits. A plurality of rollers are operatively associated with the heating apparatus. At least one rotatable belt is mounted on the plurality of rollers. The belt is adapted to thread the work-piece through the heating apparatus and remove metal scales that form and flake off the work-piece during heating. A motor is operatively connected to the rollers for driving the rollers thereby causing the belt to rotate through the heating apparatus.
In accordance with another aspect of the present invention, there is provided a metal scale removing device comprising a heating apparatus for heating a work-piece. The heating apparatus has and inlet through which the work-piece is fed and an outlet through which the work-piece exits. A plurality of rollers are operatively associated with the heating apparatus. A rotatable belt is mounted on the plurality of rollers and is adapted to catch metal scales that have fallen from the work-piece and transport the metal scales away from the heating apparatus.
One advantage of the present invention is the provision of a new threading device for induction heaters.
Another advantage of the present invention is the provision of a new and improved scale removing device for induction heaters.
Yet another advantage of the present invention is the provision of a belt rotatably disposed within an induction heater capable of effectively threading soft or limp metal material through the induction heater.
Still another advantage of the present invention is the provision of a belt rotatably disposed within an induction heater having the ability to remove metal scales that form and flake off metal materials during heating.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the detailed description of the preferred embodiment.